Changes:

- Parsing grouped expressions is now possible
- formatting

git-svn-id: https://svn.tlawal.org/svn/monkey@34 f6afcba9-9ef1-4bdd-9b72-7484f5705bac

ast/ast.go

@@ -189,6 +189,6 @@ func (ie *InfixExpression) String() string {
 }
 
 // Booleans
-func (b *Boolean) expression_node() {}
+func (b *Boolean) expression_node()     {}
 func (b *Boolean) TokenLiteral() string { return b.Token.Literal }
-func (b *Boolean) String() string { return b.Token.Literal}
+func (b *Boolean) String() string       { return b.Token.Literal }

parser/parser.go

@@ -100,6 +100,9 @@ func New(l_lexer *lexer.Lexer) *Parser {
 	l_parser.register_prefix(token.TRUE, l_parser.parse_boolean)
 	l_parser.register_prefix(token.FALSE, l_parser.parse_boolean)
 
+	// Grouped Expression
+	l_parser.register_prefix(token.LPAREN, l_parser.parse_grouped_expression)
+	
 	return l_parser
 }
 
@@ -278,3 +281,12 @@ func (l_parser *Parser) parse_boolean() ast.Expression {
 		Value: l_parser.current_token_is(token.TRUE),
 	}
 }
+
+func (l_parser *Parser) parse_grouped_expression() ast.Expression{
+	l_parser.next_token()
+	expression := l_parser.parse_expression(LOWEST)
+	if !l_parser.expect_peek(token.RPAREN){
+		return nil
+	}
+	return expression
+}

parser/parser_test.go

@@ -290,6 +290,26 @@ func TestOperatorPrecedenceParsing(l_test *testing.T) {
 			"3 < 5 == true",
 			"((3 < 5) == true)",
 		},
+		{
+			"3 < 5 == true",
+			"((3 < 5) == true)",
+		},
+		{
+			"(5 + 5) * 2",
+			"((5 + 5) * 2)",
+		},
+		{
+			"2 / (5 + 5)",
+			"(2 / (5 + 5))",
+		},
+		{
+			"-(5 + 5)",
+			"(-(5 + 5))",
+		},
+		{
+			"!(true == true)",
+			"(!(true == true))",
+		},
 	}
 	for _, tt := range tests {
 		l_lexer := lexer.New(tt.input)